Process control systems commonly employ pressure regulators (e.g., back-pressure regulators) to control or maintain a pressure of a process fluid to protect instruments or other control devices that are sensitive to high pressures. Fluid regulators such as, for example, back-pressure regulators typically include a fluid valve assembly having a pressure sensor such as a piston to sense the pressure of a pressurized fluid at an inlet of the regulator. When the pressure of the pressurized fluid at the inlet exceeds a reference or set-point pressure (e.g., provided by the fluid regulator), the pressure sensor causes a flow control member of the fluid valve to open to allow fluid flow through the regulator body between the inlet and an outlet, which may be coupled to a lower pressure system utilizing the fluid or to the atmosphere.
However, space limitations or constraints may limit the use of back pressure regulators in some applications. For example, in a gas exploration application, a tubing having, for example, a diameter of approximately 2 to 2½ inches is typically used to extract the fluid from a well. The tubing is too small to receive a conventional back pressure regulator coupled to an agent injection feed line that is disposed within the tubing.